Use ngIf for plugin tabset

This should be a very valuable performance boost and especially
much less strain on external services.
Rename isVisible to isActive and add overrider

Check the improved comment for more.
Add state.postInit()

This function launches after the stateLoaded event and adds an empty
status object to each token. This will be useful for introspection.
Allow introspection through contextMenu

The directive can now receive an object, which should usually be the
target of the context menu. This object can be made knowing that a
context menu is opened or closed.
Use ngIf to avoid unnecessary arethusaContextMenus

If a token doesn't have its context menu triggered, there is no point
to listen to its databinding. We can therefore safely remove it from
the DOM through ngIf when we don't need it.